1. Field of Invention
The present invention relates to a method of culturing an organ of Mishima-saiko, plants belonging to genus Bupleurum using their root as an explant. More specifically, the present invention relates to an improved method of culturing said organ while regulating the concentration of carbohydrate in a medium over a specific culturing period.
2. Description of Related Art
The tissue (or organ) culture of saponincontaining plants for galenical has attracted attention in terms of providing a stable supply of galenical resources. Among these, since ginseng is very expensive, extensive attempts have been made to effectively produce saponin by culturing a callus derived from a root of ginseng, Panax Schinseng Nees, or an adventitious root or hairy root thereof.
Saiko (root of Mishima-saiko) is a galenical formulated in a wide variety of Chinese medicines, and has been known to contain as its components saiko-saponin a to d comprised of triterpenoids as genin. From the viewpoint of a stable supply of the galenical resources as described above, attempts also have been made to cultivate the tissue (or organ) of the Mishima-saiko. In the production of a useful substance by tissue (or organ) culture, the contents of the useful substance are generally enhanced by hormone regulation, etc., but in the case of Mishima-saiko, it is difficult to produce saiko-saponin by callus culture (Syoyaku Gaku Zasshi (Society of Galenicals) 28 (2) pp 152-160, 1974).
On the other hand, there was also an attempt made to produce saiko-saponin with Mishima-saiko cultured root. In this case, the production of saponin was enhanced by varying the ratio of nitric ions to ammonium ions as nitrogen sources (Nippon Nogeikagaku Zasshi (Agriculture Society of Japan), 63, 35, page 496, March, 1989)
However, there has been no investigation into the influence of carbohydrates, which are the most essential components among the medium components, upon the production of saponin.
Therefore, the object of this invention is to provide an organ culturing process which enables the effective production of saiko-saponins using root of the Mishima-saiko as the explant of the same.
In the course of the examination of the culture conditions in the culturing process using the root of Mishima-saiko as an explant of same, for example, the influence of various hormones, the present inventors unexpectedly found that the regulation of the carbohydrate concentration to be added to the medium depending on the culturing periods significantly influences the productivity of saiko-saponins, to thereby achieve this invention.